LED lamp for light source of a headlamp

ABSTRACT

Whereas incandescent light bulbs and other similar light sources known in the prior art emit light in all directions, LED lamps emit light in a single direction only, and this is manifested in the problem of being unable to achieve light distribution characteristics satisfied by conventional headlamp designs. The present invention realizes an LED lamp for a light source of a headlamp disposing an LED chip  2  in the vicinity of the focus of a projection means and providing a shielding member  7  covering a portion of the LED chip  2  in a formation allowing a light distribution characteristic suitable for a vehicle front-illumination light to be obtained when light from the LED chip  2  is magnified and projected in an illumination direction by a projection lens  10  or the like constituting the projection means; accordingly, accurate light distribution characteristics can be obtained in a simple manner by projecting in the illumination direction using the projection lens  10.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to LED lamps, and in particular, to theconfiguration of LED lamps used as light sources in vehicle lights.Furthermore, it relates to the configuration of an LED lamp suitable foruse as a light source in a vehicle lamp for illumination purposes thathas not previously been put to use as headlamps (or headlights),auxiliary headlamps (or fog lights), or the like.

2. Detailed Description of the Prior Art

When LED lamps are used as a light source in flashlights and othersimilar lamps for the purpose of illumination in the prior art, a largeLED chip is housed in a large package and light amount is obtained by,for example, applying a current of between several ten and severalhundred milliamperes. Simultaneously, as the package is made large insize, deterioration or breakage of the LED chip as a result ofoverheating is prevented by effectively conducting the heat emitted inthe LED chip to the outside when it is lit and discharging it to theatmosphere or the like. (For example, see Patent Document 1)

Patent Document 1

The Japanese Patent Laid-Open No. 2000-150968 (Paragraph 0011 throughParagraph 0034, FIG. 1)

Nevertheless, when a light fixture using an LED lamp as a light sourceis employed as a vehicle lamp fixture for a headlamp or the like, strictlight distribution characteristics are set forth in relevant standardsand other regulations with regard to prevent the drivers of oncomingvehicles from being dazzled by the light directed forwards. Furthermore,the configuration of lamps for the headlamp or the like is establishedin consideration of incandescent light bulbs and other similar itemsemitting light flux uniformly in almost all directions. Consequently,problems exist in that light distribution characteristics and the likecannot be satisfied by simply replacing the lamp with an LED lampradiating light in a single direction in a relatively large amount.

SUMMARY OF THE INVENTION

As a tangible means of resolving the problems known in the prior art,the present invention realizes an LED lamp for a light source of aheadlamp characterized in that an LED chip or a white LED light emissionportion comprising an LED lamp and fluorophor is disposed in thevicinity of the focus of a projection means, and a shielding membercovering a portion of the white LED light emission portion is providedin a formation allowing a light distribution characteristic suitable fora vehicle headlamp to be obtained when light from the white LED lightemission portion is magnified and projected in an illumination directionby the projection means. Accordingly, the problems are resolved byenabling the regulated light distribution characteristics to beaccurately and easily achieved even when an LED lamp is used as a lightsource.

BRIEF DESCRIPTION OF THE DRAWINGS

These and others and advantages of the present invention will becomeclear from following description with reference to the accompanyingdrawing, wherein:

FIG. 1 is a perspective view showing an LED lamp for a light source of aheadlamp according to a preferred embodiment of the present invention.

FIG. 2 is a cross-section view on A—A of FIG. 1.

FIG. 3 is an explanatory drawing showing a typical passing lightdistribution characteristic obtained by the present invention.

FIG. 4 is an explanatory drawing showing an embodiment of the LED lampfor the light source of the headlamp according to the present inventionwhen a projection lens is assembled thereto.

FIG. 5 is a cross-section view showing a typical configuration of ashielding member in the LED lamp for a light source of a headlampaccording to the present invention.

FIG. 6 is an explanatory drawing showing typical chromatic aberrationoccurring in the projection lens.

FIG. 7 is a cross-section view showing another typical configuration ofthe shielding member in the LED lamp for the light source of theheadlamp according to the present invention.

FIG. 8 is a cross-section view showing a further typical configurationof the shielding member in the LED lamp for the light source of theheadlamp according to the present invention.

FIG. 9 is an explanatory drawing showing a typical configuration of theheadlamp light when a plurality of LED lamps for the light source of theheadlamp and projection lenses are combined.

FIG. 10 is an explanatory drawing showing a typical shaping method for alight distribution characteristic when a plurality of LED lamps for thelight source of the headlamp and projection lenses are combined.

FIG. 11 is an explanatory drawing showing a configuration when the LEDlamp for the light source of a headlamp according to the presentinvention is combined with a reflector.

REFERENCES

1: LED lamp for a light source of a headlamp

2: LED chip

3: Base unit

3 a: Base

3 b: Lead frame

3 c: Insulating layer

4: Metal wire

5: Fluorophor

6: Window glass member

7: Shielding member

7 a: Serrated section

8: White LED light emission portion

9: Silicone gel

10: Projection lens

11: Reflector

12: SiO₂ film

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the present invention will be described by way of preferredembodiments thereof with reference to the accompanying drawings. Thepart indicated by reference 1 in FIG. 1 and FIG. 2 is an LED lamp for alight source of a headlamp according to the present invention(hereinafter referred to as an “LED lamp 1”), and in the LED lamp 1, anLED chip 2 is mounted on a base unit 3.

The base unit 3 provides a base 3 a formed with a metal member of copperor some other metal excellent in heat conduction and a lead frame 3 balso formed with a metal member. The base 3 a and the lead frame 3 b areinsulated by an insulating layer 3 c formed with a resin member oranother similar insulating member. The LED chip 2 mounted on the base 3a is wired to the lead frame 3 b using a metal wire 4 or the equivalent,so the lighting can be carried out using power supplied from theexterior.

Considering the conditions to be satisfied for usage of the LED lamp 1as a light source for a headlamp, it can be seen that the regulatedcolor of the lamp is white or monochromatic yellow. Although white lightis used more often, no LED chip 2 that can directly emit white lightactually exists, and fluorophor 5 are used in combination in order toobtain white light.

As a first method of doing so, an LED chip 2 generating blue light and awavelength conversion member such as fluorophor 5 emitting yellow lightare combined, and white light is obtained by mixing the blue lightemitted directly from the LED chip 2 with the yellow light emitted fromthe fluorophor 5 excited by the light from the LED chip 2. As a secondmethod, furthermore, the LED chip 2 emitting ultra-violet light iscombined with fluorophor 5 emitting light of the three primaries red(R), green (G), and blue (B). In this case, the light emitted directlyfrom the LED chip 2 is not used as illumination light, and theillumination light from the LED lamp 1 comprises the light emitted fromthe fluorophor 5.

The present invention will hereinafter be described in terms of a lightsource for a headlamp using a white LED light emission portion 8combining an LED chip 2 and fluorophor 5; nevertheless, in situationswhere it is required that the lamp color be yellow, for example, it ispossible for the light emitted directly from the LED chip 2 to be usedas the light for the light source. In such a situation, however, it isalso possible for the present invention to be implemented, and it issufficient for the white LED light emission portion 8 to be replaced bythe LED chip 2 in this case.

Parts such as the LED chip 2, a metal wire 4, and fluorophor 5 aremechanically weak and do not have good resistance to humidity and othersimilar factors. Accordingly, these parts are covered by a lens-shapedmember formed from transparent resin or the like or by a window glassmember (the accompanying drawings show an example in which a windowglass member 6 is used), and through the action of this part and thebase 3 a, are sealed with respect to outside air. Thus, theabove-described parts are prevented from breaking as a result of contactwith the other parts, deteriorating as a result of humidity, and othersimilar factors. Furthermore, it is preferable to fill inert gas,silicone gel, or the like (this explanation assumes usage of siliconegel 9) into the space between the lens-shaped member or the window glassmember and the white LED light emission portion 8.

In addition, the LED lamp 2 according to the present invention providesa shielding member 7. Furthermore, this shielding member 7 covers aportion of the fluorophor 5, and for example, when light emitted fromthe fluorophor 5 is projected in the illumination direction by aprojection lens or the like, allows a light distribution pattern forpassing or any other desired light pattern to be obtained.

Accordingly, both the window glass member 6 and the shielding member 7are disposed more forward than the fluorophor in the illuminationdirection, and since the window glass member 6 is transparent and theshielding member 7 is opaque, either of these parts can be disposedforward of the other. Furthermore, the shielding member 7 can be freelyformed, for example, using the inner and outer surfaces of the windowglass member 6 with an opaque paint covering or vapor deposition ofmetallic member.

When a headlamp using the LED lamp 1 as a light source is used toprovide light for an infrared night-vision device, a member transmittingthe infrared light and shielding visible light-is used for the windowglass member 6, and in terms of the shielding member 7, it is sufficientto use a member shielding beam of light from infrared through visiblelight. Moreover, when the shielding member 7 is a vapor deposited filmwith the metallic member, deterioration as a result of oxidation andother similar factors are considered possible, and therefore, it isacceptable to provide protection by covering with a SiO₂ film asindicated by reference 12 in FIG. 2.

Reference HB from FIG. 3 indicates a typical passing light distributionpattern for left-hand drive situations. In this passing lightdistribution pattern HB, the half on the right of the vehicle centerlineconstitutes a light distribution pattern containing no upward directedlight in order to prevent the drivers of oncoming vehicles from beingdazzled. On the other hand, the half on the left of the vehiclecenterline contains a section called an “elbow” in which upward directedlight increases towards the left at an angle of 15.degree. in order toallow traffic signs and the like on the road side to be easilyidentified.

In the present invention, the shape of the portion of the fluorophor 5not covered by the shielding member 7 is made similar to that of theabove-mentioned passing light distribution pattern HB. Moreover, asshown in FIG. 4, the shape of the fluorophor 5 obtained in this way isprojected in the illumination direction P by a projection lens 10 toobtain the passing light distribution pattern HB. In order to ensurethat highest intensity is in the front horizontal direction so that goodlong-distance visibility can be assured, when the LED chip 2 is coveredby the shielding member 7, this is performed at the point of highestintensity or at a position in the vicinity thereof.

Horizontal and vertical inversion occurs after projection by theprojection lens 10, and therefore, the LED lamp 1 is mounted in theheadlamp in a 180.degree.-rotated condition, and when projection iscarried out by the projection lens 10 in this condition, an erect imageof the passing light distribution pattern HB can be obtained.Furthermore, by modifying the formation of the shielding member 7, lightdistribution patterns without an elbow, light distribution patterns fordriving, and other types of light distribution pattern can be freelyformed.

As a further description of the shielding member 7, it can be statedthat since the shielding member 7 shields the light from the LED chip 2,when half thereof is covered, the quantity of light is halved, and inthis way, loss occurs with respect to the quantity of light emitted fromthe LED chip 2. The results of studies by the inventors show that thetreatment of the surface at least opposing the LED chip 2 has a minoreffect on the shape of the light distribution characteristic formedafter projection.

That is to say, when the surface of the shielding member 7 (i.e., thesurface facing the projection lens 10) reflects light, this light isre-projected by the projection lens 10 and there is a high probabilitythat formation of the light distribution pattern will be adverselyaffected. Therefore, it is preferable to provide non-reflectiontreatment of a color such as black. Nevertheless, a mirror finish isprovided to the rear surface, and even when the light emitted from theLED chip 2 is reflected, this returns only to the LED chip 2 side andhas no substantial effect on the formation of the boundary between thefluorophor 5 and the shielding member 7, or in other words, on theformation of the shape of the light distribution characteristic.

The light reflected by the rear surface of the shielding member 7 isreturned to the inside of the fluorophor 5. Therefore, by providing, asshown in FIG. 5, a mirror finish on the rear surface of the shieldingmember 7 and, for example, a serrated section 7 a emitting light to bereflected in the direction of the non-covered portion of the fluorophor5, the brightness of light from the fluorophor 5 can be improved. Inother words, the light reaching the rear surface of the shielding member7 can be collected for use as illumination light, and it has beenconfirmed by trial manufacture and measurement by the inventors that thequantity of light increases by at least 15%.

Furthermore, results of simultaneous studies carried out by theinventors regarding the shielding member 7 showed that it is preferableto perform projection with the focus of the projection lens 10 alignedwith the shielding member 7 in order to enable more precise formation ofthe shape of the light distribution characteristic. Moreover, whenbrightness is required within the light distribution characteristic, itis preferable to perform projection with the focus of the projectionlens 10 aligned with the white LED light emission portion 8 (or LED chip2 when the lamp color is yellow). If the LED chip 2 and the shieldingmember 7 are disposed in mutual proximity, the focus is substantiallyaligned with both parts, and this condition is favorable in terms ofboth shape and brightness. Furthermore, a gap between both of theseparts of 2 mm or less is preferable, and more favorable results can beobtained by reducing this gap to 1 mm or less.

In situations as explained above where the white LED light emissionportion 8 covered by the shielding member 7 is projected by theprojection lens 10, a single plano-convex lens is often used for theprojection lens 10. Therefore, as shown in FIG. 6, a difference occursin the position of, for example, the focus fb for blue light and thefocus fr for red light, resulting in what is known as chromaticaberration.

In such a case, if the shielding member 7 is disposed closer to any oneof such foci, coloration occurs in the terminator HL (see FIG. 3)corresponding to the portion of the passing light distribution patternHB in which the shape of the shielding member 7 is projected, and it istherefore impossible to satisfy the regulation requiring that the lightcolor be monochromatic. As a means of solving this problem, if thethickness t of the shielding member 7 is, for example, made to extendfrom the focus fb for the blue light to the focus fr for the red lightas shown in FIG. 7, and a plurality of colors are emitted on theprojected terminator HL, the color of the light emitted when this pluralcolors are mixed is close to white. Thus, it is possible to eliminate asense of specific colors being present.

Alternatively, as shown in FIG. 8, two or more thin shielding members 7are provided, and for example, the front and rear surfaces of the windowglass member 6 are used; furthermore, one of these thin shieldingmembers 7 is disposed at the position of the focus fb for the bluelight, and the other is disposed at the position of the focus fr for thered light. In accordance with this configuration, the blue light and thered light having a substantially complimentary-color relationship aremixed on the projected terminator HL of the passing light distributionpattern HB, and in the same way as explained above for the thickshielding member 7, it is possible to eliminate a sense of specificcolors being present.

As a further description of the shielding member 7, it can be statedthat in addition to the chromatic aberration described above, aberrationfactors such as spherical aberration, astigmatism, coma, fieldcurvature, and distortion occur in the projection lens 10. As a resultof these aberration factors, shape distortion or focus displacementoccurs when the shape of the white LED light emission portion 8 isprojected.

Therefore, if the shielding member 7 is formed with the same curvatureas the curvature in the focus surface of the projection lens 10 in orderto countermeasure field curvature for example, it is possible to obtaina sharp terminator HL extending from the center to the right and left(provided that spherical aberration, astigmatism, and coma have noeffect). Furthermore, in response to distortion and other aberrationfactors that cause shapes to become distorted, it is sufficient tocorrect the shielding member 7 in such a way that the desired shape ofthe passing light distribution pattern is obtained after projection.

As explained above, all aberration factors can be resolved by methodssuch as thickening, curving, or transforming of the shielding member;however, no detailed explanation of these methods will be providedherein as such information is already publicly known in terms of a widerange of projector-type lamps using projector lenses 10.

FIG. 9 shows a schematic representation of another embodiment of aheadlamp lamp using an LED lamp 1 as a light source according to thepresent invention. FIG. 4 showed an illumination-lamp configurationcomprising a single LED lamp 1 and a single projection lens 10; however,while the white LED light emission portion 8 containing the shieldingmember 7 satisfies the regulations for the passing light distributionpattern HB in terms of shape, the illumination distribution providesinsufficient central illumination and other similar regulations may notbe satisfied.

Here, as the white LED light emission portion 8 with an extremely smallsurface area is directly projected in the present invention, theprojection lens 10 may also be small. Accordingly, even if a pluralityof combinations of an LED lamp 1 and the projection lens 10 areprovided, the dimensional requirements for a headlamp can be satisfied.

Accordingly, this embodiment sets the plurality of combinations of theLED lamp 1 and the projection lens 10 to, for example, three for asingle illumination lamp. In this case, the LED lamp 1 can be from thesame one used in the previous embodiment. However, as for the projectionlens 10, a No. 1 projection lens 10 a with a same magnification as theprojection lens 10 used in the FIG. 4, a No. 2 projection lens 10 b witha reduced magnification, and a No. 3 projection lens 10 c with a furtherreduced magnification are provided. All of these projection lensesperform projection in the same direction.

FIG. 10 shows the passing light distribution pattern HBs obtained from aheadlamp configured as explained above. Although this passing lightdistribution pattern HBs is same to the passing light distributionpattern 1B (see FIG. 3) from the previous embodiment in terms of shape,it is formed into a prescribed shape by superimposing the lightdistribution pattern Ha from the No. 1 projection lens 10 a, the lightdistribution pattern Hb from the No. 2 projection lens 10 b, and thelight distribution pattern Hc from the No. 3 projection lens 10 a–c.

Accordingly, the light distribution pattern Hc from the No. 3 projectionlens 10 c having the lowest magnification is the brightest. Moreover, bydisposing this light distribution pattern Hc in the central area of thepassing light distribution pattern HBs, illumination for the frontdirection of a vehicle becomes brightest and long-distance visibility isimproved. Furthermore, regulations can be satisfied by adjusting themultiplicity of combinations of an LED lamp 1 and a projection lens 10and the magnification of the corresponding projection lenses 10 c.

In general, the quantity of light obtained from the LED lamp 1 is smallin comparison with that of the halogen bulbs and metal halide dischargedlamps used as light sources in the prior art. Therefore, such a methodof increasing the number of combinations and the quantity of light isvery effective as a means of realizing the headlamp using the LED lamp 1as a light source.

In order to simplify the above explanation, the embodiment obtains thefinal passing light distribution pattern by superimposing a plurality oflight distribution patterns having a substantially identical shape anddifferent magnifications. However, the final passing light distributionpattern may be formed by joining a plurality of elements suitablydividing the shape of the final passing light distribution pattern. Inother words, it is sufficient to ultimately obtain the lightdistribution pattern that satisfies the regulations.

FIG. 11 shows an example of another projection method using the LED lamp1 according to the present invention. In this example, projection in theillumination direction P is carried out using, for example, a reflector11 having a paraboloid of revolution shape or another similar shapehaving a focus instead of the projection lens 10 constituting theprevious projection means, thus realizing an illumination light with theprescribed light distribution pattern.

Accordingly, this projection method using the reflector 11 forming aprojection image using the reflected light disposes the LED chip 2, thefluorophor 5, the shielding member 7, and the like in opposition to thereflector, or in other words, the parts are disposed in proximitythereto facing approximately backward with respect to the illuminationdirection P.

If this reflector 11 is, for example, a multi-reflector combining aplurality of parabolic adjustable surfaces, a high degree of freedom isachieved when forming the passing light distribution pattern HB, andsince the chromatic aberration does not fundamentally occur in thereflector 11, the high quality passing light distribution pattern HB canbe easily obtained. Furthermore, as in the case of the projection lensexplained above, a plurality of combinations of the LED lamp 1 and thereflector 11 can be used in the realization of the headlamp.

As explained above, the present invention realizes an LED lamp for alight source of a headlamp disposing an LED chip in the vicinity of thefocus of a projection means and providing a shielding member covering aportion of the LED chip in a formation allowing a light distributioncharacteristic suitable for a headlamp of a vehicle to be obtained whenlight from the LED chip is magnified and projected in an illuminationdirection by the projection means. Accordingly, light distributionshapes with accurate characteristics can be obtained in an extremelysimple manner by projecting the shape of the light emission portion ofthe solid construction constituted by the LED lamp for a light source ofa headlamp in the illumination direction using a projection lens or areflector, and thus, exceptional advantages are achieved in the form ofreliability improved by the solid state light source, cost reduction bythe simplified construction, and the ability for compact designs.

While the presently preferred embodiment of the present invention hasbeen shown and described, it will be understood that the presentinvention is not limited thereto, and that various changes andmodification may be made by those skilled in the art without departingfrom the scope of the invention as set forth in the appended claims.

1. An LED lamp for a light source of a headlamp having a projection means which has a focus, characterized in a combination of a light source selected from the groups consisting of an LED chip and a white LED light emitter, and a fluorophor, the light source and fluorophor disposed in the vicinity of the focus of the projection means, and a shielding member covering a portion of said light source in a shape allowing a light distribution characteristic suitable for a headlamp of a vehicle to be obtained when light from said light source is magnified and projected in an illumination direction by said projection means; wherein a surface of said shielding member opposing the light source has a mirror finish that is inclined for reflecting light in the direction of a non-shielded portion of the light source.
 2. The LED lamp for the light source of the headlamp of claim 1, further characterized in that said shielding member is disposed to form a gap of 2 mm or less from said light source.
 3. The LED lamp for the light source of headlamp of claim 1 or 2, further characterized in that said shielding member shields the portion of said light source in which highest intensity occurs or of an edge in the vicinity thereof.
 4. The LED lamp for the light source of headlamp of claim 1 or 2, further characterized in that a wavelength conversion member is interposed between said light source and said shielding member.
 5. The LED lamp for the light source of the headlamp of claim 1 or 2, further characterized in that a lens member or window glass member covering said light source is integrated with said shielding member. 